Optimizing district heating networks

Abstract

District heating networks (DHNs) are essential for decarbonizing building energy demand and are expected to play a larger role in future energy systems. Optimizing DHN design is vital as it directly impacts system cost and performance. Current optimization methods focus on minimizing cost without considering technical performance or its impact on its end-users. In some regions, there is limited social acceptance for DHN due to poor technical performance, highlighting the need to integrate consumer-oriented performance criteria in the design phase. This study proposes a DHN optimization method that explicitly incorporates user-level performance when evaluating different DHN designs. Two design strategies-a cost-optimal design and a maximum-efficiency design-are compared across 100 small, randomly generated DHNs and on a large real-world case. For small DHNs, the cost associated with efficiency improvements shows high variability. Only 6% of cases exhibit a cost increase below 10% per 1% efficiency gain, and only 3% are within the range of 0.5-2%. In the large DHN case, efficiency optimization increases the network’s efficiency from 56.5% to 69.7% at 18% cost increase. Efficiency-oriented designs significantly reduce consumer exposure to thermal discomfort under cold outdoor conditions or heat-source disturbances, and require less energy to meet demand. As network efficiency can potentially yield great benefits for consumers in the DHN, focusing solely on cost optimization is shortsighted. More emphasis on network efficiency may increase social acceptance of DHN and by that accelerate the energy transition.